Expression of functional purinergic receptors in pulmonary neuroepithelial bodies and their role in hypoxia chemotransmission

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Abstract
Adenine nucleotides act through specific cell surface receptors to invoke a variety of biological responses. Here we show that cells of neuroepithelial bodies (NEB), presumed O2 airway sensors in neonatal hamster lung, express functional P2X receptors (P2X-R). Positive immunostaining was detected in NEB cells using double-label immunohistochemistry with antibodies against P2X2 and P2X3 receptor subunits, which co-localized with serotonin (5-HT), a marker of NEB cells. For electrophysiological characterization of P2X2-R in NEB cells, fresh neonatal hamster lung slice preparation was used. Under whole-cell patch clamp, perfusion with ATP induced a concentration-dependent, non-desensitizing inward current (EC50=12 microM). Perfusion with alpha,beta-methylene ATP also induced a slow-desensitizing inward current (EC50=8.2 microM). Suramin (IC50 ca. 43 microM) and TNP-ATP (IC50 ca. 8 microM) blocked the currents evoked by both ATP and alpha,beta-methylene ATP. Using carbon fiber amperometry we observed that hypoxia and ATP induced 5-HT release from NEB cells and that this release was blocked by suramin. These data suggest that functional P2X2/3 heteromeric receptors are expressed in NEB cells. The possible function of these purinoreceptors in NEB cells could include modulation of hypoxia chemotransmission.